GEAR MECHANISM, ESPECIALLY FOR A DOUBLE SCREW EXTRUDER

ENGRENAGE, EN PARTICULIER POUR EXTRUDEUSE A DEUX VIS

English Abstract

The invention relates to a gear mechanism, especially for a double screw
extruder, comprising a drive shaft, at least one down-step stage for a change
in speed and rotational torque adapted according to the purpose of the
application, a torque division stage, and two driven shafts to which the
torque divided in the division stage is transmitted. According to the
invention, an intermediate shaft (8) is arranged downstream from the torque
division stage (7,9). Part of the torque is transmitted to said intermediate
shaft. Helical toothed gear wheels (11) are arranged in an opposite direction
on the intermediate shaft (8) and engage with gear wheels (14,15) located on
the first driven shaft (13), neutralising axial force in a manner similar to
double helical gearing. The second driven shaft (10) is directly driven out of
the torque division stage (7,9) and guided in sliding bearings (18).

French Abstract

L'invention concerne un engrenage, en particulier pour extrudeuse à deux vis, comportant un arbre d'entraînement, au moins une étage réducteur comportant l'arbre d'entraînement, destiné à faire varier le nombre de tours et le couple en fonction du but d'utilisation, un étage de division de puissance et deux arbres de sortie auxquels la puissance divisée dans l'étage de division de puissance est transmise. Selon l'invention, au moins un arbre intermédiaire (8) est monté en aval de l'étage de division de puissance (7, 9), une partie de la puissance étant transmise à cet arbre intermédiaire. Des roues dentées (11, 12), dont les dentures hélicoïdales sont disposées en sens opposé, sont placées sur l'arbre intermédiaire (8), sont en prise avec des roues dentées (14, 15) se trouvant sur le premier arbre de sortie (13) et ont un effet correspondant à la compensation des forces axiales d'une denture à chevron. Le second arbre de sortie (10) est entraîné directement par l'étage de division de puissance (7, 9) et guidé dans des paliers lisses (18).

Claims

Claims
1. Transmission, especially for twin-screw extruders, with
a driveshaft and at least one reduction stage that includes the
driveshaft and adapt the speed and torque to various
applications, an output-bifurcating stage, and two output shafts
that the output divided in the output-bifurcating stage is
transmitted to, characterized by at least one intermediated shaft
(8) downstream of the output-bifurcating stage (7 & 9) that at
least some of the output is transmitted to, by opposingly cogged
gearwheels (11 & 12) mounted on the intermediate shaft (8),
engaging gearwheels (14 & 15) mounted on the intermediate shaft
and, like herringbone cogs, relieving axial forces, and in that
the second output shaft (10) is mounted in sliding bearings (18)
and driven directly from the output-bifurcating stage.
2. Transmission as in Claim 1, characterized in that the
output shafts (10 & 13) rotate in the same sense.
3. Transmission as in Claim 1 or 2, characterized in that
the intermediate shaft (8) and one output shaft (13) are
sectioned and the sections connected by a clutch (16 & 17).
4. Transmission as in Claim 1, 2, or 3, characterized in
that the output is distributed to the intermediate shaft (8)
-8-

and one output shaft (10) by way of gearwheels (7 & 9) that
directly engage each other and in that the intermediate shaft (8)
meshes with another output shaft (13) by way of gearwheels (11,
12, 14, & 15).
5. Transmission as in Claim 1 or 2, characterized in that
the sliding bearings (18) cultivate a hydrodynamic film of
lubricant.
6. Transmission as in Claim 5, characterized in that the
slide-over surface of the sliding bearings (18) has a coat of
lubrication that functions in particular in the combined-friction
range.
7. Transmission as in Claim 5, characterized by depressions
(20) in the slide-over surface of the sliding bearings (18).
8. Transmission as in Claim 7, characterized in that the
depressions (20) are channels (21).
9. Transmission as in Claim 8, characterized in that the
channels (21) extend essentially parallel and at an angle to the
radial plane.
-9-

Description

CA 02313079 2000-06-O5
1 TRANSMISSION, ESPECIALLY FOR TWIN-SCRBW EXTRUDER
2 The present invention concerns a transmission, especially for twin-screw
3 extruders, with a driveshaft, at least one reduction stage, an output-
4 bifurcating stage, and two output shafts. The reduction stage or stages
adapt the speed and torque to various applications. The transmission is
6 recited in the preamble to Claim 1.
7
8 A transmission for twin-screw extruders of this genus is known from
9 European Patent A 0 670 495. It includes a driveshaft and at least one
output shaft. The output shaft is driven by the driveshaft by way of at
11 least one helical driving gearwheel mounted thereon and by way of at
12 least one helical output gearwheel mounted on the output shaft. The
13 gearwheels engage axially movable and helical intermediate gearwheels.
14 The intermediate gearwheels are associated with an axial-force
compensator. This transmission distributes the load adequately between
16 the two intermediate gearwheels ~t is complicated and takes up
17 considerable space.
18
19 The object of the present invention is accordingly a completely advanced
transmission of the aforesaid genus that will occupy less space and
21 reliably transmit even powerful torques at a speed appropriate for the
22 particular application.
23
24 This object is attained as recited in Claim 1.

CA 02313079 2000-06-OS
1 The advantage of the present invention is that, since the sliding
2 bearings occupy less space, the axes of the individual shafts can
3 be closer together even though an equivalent torque is
4 transmitted. It will, however, also be possible to transmit more
powerful torques without varying the distance between the shafts
6 by using longer-diameter shafts or gearwheels or, if the shafts
7 lack sliding bearings, larger radial bearings.
8
9 The output shafts in one preferred embodiment of the present
invention,.rotate in the same sense. This embodiment can be
11 employed to drive a twin-screw extruder~with screws that~rotate
12 in the same sense.
13
14 The two output shafts can be even closer~together if.at~least one
intermediate shaft is -interposed downstream of the output-
16 bifurcating stage and can accommodate at least some of the
17 transmitted output. Such an arrangement will also allow the
18 rotation to be reversed.
19
The advantage of closer-together output shafts can also be
21 attained if the intermediate shaft merges directly into one of
22 the output shafts.
23
24 It will also be possible for the intermediate shaft and one
2

CA 02313079 2000-06-OS
1 of the output shafts to engage each other directly by way of
2 gearwheels. This arrangement will allow further transmission of
3 output in the opposite sense.
4
In one practical embodiment of the present invention, opposingly
6 cogged helical gearwheels are mounted the other on the
7 intermediate shaft and one on the output shaft, creating a
8 herringbone gearwheel that eliminates axial force. The result is
9 a distribution of output followed by addition, the output
components being precisely equal. This distribution of output
11 allows more gearwheels and bearing.to be employed, decreasing the
12 load on the individual components. Another advantage is that the
13 intermediate shaft and the output shaft can be sectioned and
14 connected by a clutch. .
16 The output in one preferred embodiment of a transmission with
17 output shafts that rotate in the same sense is distributed
18 between an intermediate shaft and a output shaft by way of
19 directly mutually engaging gearwheels, the intermediate shaft
meshing with another output shaft by way of other gearwheels.
21
22 A hydrodynamic film can be created to make them stronger by
23 lubricating the sliding bearings.
24
This special film on the bearings' surface will allow
3

' CA 02313079 2000-06-OS
1 reliable operation even in a combined-friction range.
2
3 Depressions in the bearings surface can promote formation of the
4 film. To improve introduction of the lubricant and hence promote
heat removal, the depressions can be channels. If the channels
6 extend at an angle to the radial plane, the dragging flow of the
7 lubricant can be exploited to remove even more heat, eliminating
8 the usual need for to supply oil under pressure.
9
The present invention will now be specified with reference to the.
11 attached drawing, wherein
12
13 Figure 1 is an opened schematic representation of a transmission
14 in accordance with the present invention,
'
16 Figure 2 illustrates in principle how the sliding bearings are
17 installed in the transmission,
18
19 and
Figure 3 illustrates appropriate structures for the surfaces of
21 sliding bearings employed in a transmission in accordance with
22 the present invention.
23
24 The transmission for a twin-screw extruder illustrated in
4

' CA 02313079 2000-06-OS
1 Figure 1 comprises a main transmission section 1 and an
2 intermediate transmission section 2. Power is supplied to a
3 driveshaft 3 by way of a pinion 4. Pinion 4 meshes with a
4 gearwheel 6 on another shaft 5. An output-distributing pinion 7
on shaft 5 engages an intermediate pinion 9 on an intermediate
6 shaft 8. The output from shaft 5 is bifurcated and distributed
7 between intermediate shaft 8 and a output shaft 10 by way of
8 output-distributing pinion 7 and intermediate pinion 9.
9 Mounted on intermediate shaft 8 in the vicinity of intermediate
transmission section 2 are two opposingly cogged gearwheels 11
11 and 12 that engage two similarly cogged gearwheels l4 and 15
12 mounted on another output shaft 13. Intermediate shaft 8 and
13 output shaft 13 are composed of-sections interrupted between
14 gearwheels 11 and.l2 and 14 and 1 gearwheels 14 and 15 and
'15 connected by clutches 16 and 17, as will be evident from Figure
16 2.
17
18 As will also be evident from Figure 2,,output shaft 10 is
19 accommodated in sliding bearings 18 and output shaft 13 in roller
bearings l9. Sliding bearings can also be provided for one or
21 more additional shafts within the scope of the present invention.
22 When for example output shafts 10 and 13 are accommodated in
23 sliding bearings, the shafts can be closer together axially and
24 still transmit the same torque.
5

CA 02313079 2000-06-OS
1 Figure 3 illustrates structures appropriate for sliding-bearing
2 surfaces. Disconnected depressions 20 for example can be
3 introduced into such a surface, extensively eliminating any
4 exchange of lubricant between the depressions. The depressions
can, however, alternatively constitute channels 21 that transport
6 the lubricant, increasing the removal of heat. To ensure a well
7 defined circulation of lubricant, channels 21 can extend
8 essentially.parallel and.at an. angle to the radial plane.
9
11
12
13
14
16
17
18
19
21
22
23
24
i
6

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